Re: How to filter external OSPF routes from database ?

Tom,
I checked,if area is nssa, then you can filter either on actual ASBR or ABR
by using the same cmd (pl test and verify). in ASBR case, it take lsa type-7
out from DB and at ABR it takes lsa-5 out of database but lsa-7 still
remains in DB which means that nssa will have this route and rest of the
areas will not. If we run it on actual ASBR then whole ospf domain will not
have the routes which were re-distributed.

On Tue, Nov 10, 2009 at 7:27 PM, Tom Solski <tom.solski_at_gmail.com> wrote:

> Thanks Miroslav. Summary address on R2 works if area 1 is configured as not
> so stubby (NSSA). I am referring to this topology:
>
> R1------area1-----R2-----area0------R3--------area2--------R4
> R1 redistributes external 1.0.0.0/8 into area1.
>
> IOS appears to me really inconsistent here. Why summary-address works for
> N2
> routes and does not for E2 routes?
>
>
> -----Original Message-----
> From: Miroslav Kosut [mailto:miroslav.kosut_at_gmail.com]
> Sent: 10-Nov-09 16:22
> To: Tomasz Solski
> Cc: Cisco certification
> Subject: Re: How to filter external OSPF routes from database ?
>
> Stubby area :-)
>
> External LSAs (LSA5) can be filtered on ASBRs using summary-address
> NET MASK not-advertise. I don't know about any other way of filtering
> them on ABRs except using stubby areas.
>
> Regards,
> Miroslav
>
> On Nov 10, 2009, at 10:15 PM, Martin Hogan wrote:
>
> > What does the Cisco Doc tell you about that command?
> >
> > Hint: It's only effective on a particular LSA type.
> >
> >
> >
> > On Tue, Nov 10, 2009 at 7:44 AM, Tomasz Solski
> > <tom.solski_at_gmail.com> wrote:
> >
> >> How to filter external OSPF routes from database ?
> >>
> >> Here is an example:
> >>
> >> R1------Ar0------R2------Ar1-------R3
> >>
> >> R1 redistributes routes into Area 0.
> >>
> >> I want ot configure R2 so R3 does not have a specific external
> >> route in its
> >> database.
> >>
> >> I tried on R2:
> >> <<<
> >> ip prefix-list R1toR3 seq 5 deny 1.1.12.0/24
> >> ip prefix-list R1toR3 seq 10 permit 0.0.0.0/0 le 32
> >> router ospf 1
> >> area 1 filter-list prefix R1toR3 in
> >>>>>
> >>
> >> but it looks like external routes can not be filtered with filter
> >> list. As
> >> soon as I advertise 1.1.12.0/24 on R1, instead of redistributing
> >> it, it
> >> disappears from R3's database and routing table.
> >>
> >>
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Received on Wed Nov 11 2009 - 11:01:43 ART